The present invention relates to sacrificial anodes and in particular sacrificial anodes for use in providing cathodic protection of buried steel products.
Sacrificial anodes for the protection of buried steel or submerged steel products is well known. The most common sacrificial anodes are made of zinc or magnesium and an electrical connector serves to connect the anode with the steel to be protected. The soil environment and/or water provides an electrolyte between the product to be protected and the anode, thus completing the circuit and the anode is sacrificed in preference to the steel. This will continue until the anode is depleted and the expected life of the anode will be a function of at least the size of the product being protected and the environment in which it is placed. The voltage potential used to drive the circuit is primarily a function of the material of the anode and the product being protected.
In other cases, an implied current system can be used where power from an external source supplies the voltage potential between an electrode and the product to be protected and typically implied current systems operate with a voltage of about 3000 mv. The standard zinc anode has an output of about 500 mv negative with respect to steel, whereas magnesium anodes would produce about 800 mv relative to steel. The zinc anode is preferred due to its higher efficiency and longer expectant life; however in some environments, it is beneficial to use the higher output magnesium anode.
It is common with sacrificial anodes to encase them in a porous material which tends to retain water such as a gypsum bentonite mixture, and in other cases, this mixture is placed between the anode and the steel or iron article to be protected.
It would be desirable to be able to manufacture a sacrificial anode in accordance with a desired voltage potential with the anode custom designed to the application, and furthermore, it would be desirable to have a sacrificial anode where the output is substantially higher than the common zinc and magnesium sacrificial anodes now used.